Controllable semiconductor components like MOSFETs (Metal Oxide Semiconductor Field-Effect Transistors), IGBTs (Insulated Gate Bipolar Transistors), J-FETs (Junction Field-Effect Transistors) etc. are widely used as electronic switches for switching electrical loads or as electronic switches in all types of switching converters. Many controllable semiconductor components include a semiconductor body with a drain region, a drift region adjoining the drain region, and a source region, each having a first conductivity type, and a body region arranged between the drift region and source region of a second conductivity type. A gate electrode serves to control a conducting channel in the body region between the source region and the drift region. The source region is electrically connected to a source electrode which is also connected to the body region, and the drain region is electrically connected to a drain electrode.
In order to realize the electrical connection between the source region and the source electrode, in many controllable semiconductor components the source electrode has a protrusion that extends into a trench of the semiconductor body where it contacts the source region. In other controllable semiconductor components, polycrystalline silicon is arranged in a trench of the semiconductor body and electrically contacts both the source region and the source electrode. In both cases, the respective trench is frequently referred to as “contact trench”. In conventional methods for producing such a controllable semiconductor component, the contact trench is temporarily sealed with a protective varnish or with polycrystalline silicon so as to allow for the processing of other elements of the semiconductor component to be produced without adversely affecting the source region or the contact trench. However, the mentioned sealing techniques require a number of process steps which on the one hand increase the production costs and on the other hand constrains a reduction of the structure size the like cell pitch of a cell structure of the transistor etc.
Hence, there is a need for an improved method for producing a controllable semiconductor component.